Spring mattresses, upholstery seats and the like



July. 7,- 1959 E. H. FRISELL 2,893,018

SPRING MATTRESSEZS, UPHOLSTERY SEATS AND THE LIKE Filed Nov. 8, 1954 5Sheets-Sheet l 'zzz 4 3 9 I Inventor EH.E z.$e-LL July 7, 1959 v E. H.FIRISELL 2,893,018

SPRING MATTRESSES, UPI-IOLSTERY SEATS AND THE LIKE Filed Nov. 8, 1954 5Sheets-Sheet 2 9 I I I V July 7, 195-9 E. H. FRISELL 2,893,018

SPRING MATTRESSES, UPHOLSTERY SEATS AND THE LIKE.

Filed Nov. 8, 1954 5 Sheets-Sheet 5 L 12 1 I w '1 ain/Z221 U d s P o 92,893,018

used as a seat and bed. This factor is not satisfied by 2,893,018present-day constructions of spring bottoms that are so SPRINGMA'I'TRESSES, UPHOLSTERY SEATS AND THE LIKE Erik Hjalmar Frisell,Lidingo, Sweden, assignor to Kommanditbolaget Irving & Frisell,Nykoping, Sweden, a corporation of Sweden Application November 8, 1954,Serial No. 467,528

Claims priority, application France March 18, 1950 6 Claims. (Cl. -247)The present invention relates broadly to the art of furniture.

More particularly, this invention relates to a spring support for use insupporting mattresses, upholstered cushions or the like on beds, chairs,settees, sofas and other comparable articles of furniture.

The invention relates to such a spring support that can be usedindependently of any overlying cushions or mattresses.

This application is a continuation in part of my prior filed applicationSerial Number 215,209, filed March 13, 1951, now abandoned, and entitledSpring Mattresses, Upholstery Seats and the Like.

It has now been established that lumbago and other backaches and kindredpains very often arise from the manner in which the backbone issupported during sleep. It is a well known fact that a great number ofsupporting structures in beds are improper and that the backbone, whenthe person is at rest, in unnaturally bent or strained. This occursbecause the bed is deformed in the central portion under the weight ofthe sleeping person so that the central portion of the body supportingsurface is, somewhat like a hammock, lower in the middle than at itsend. Corrective measures have been proposed such as by inserting a bedboard between the mattresses and the springs. However, sleeping over abed board is not very comfortable unless the mattress is of extrathickness and consequently very expensive. For this reason bed boardsand other orthopedic appliances will be used only in cases of necessityand will not attain extensive use by the general public.

On the other hand, in practically all of thepresent bed springconstructions in which the supporting surface, in the longitudinaldirection of the bedstead, is connected to end frames, which sooner orlater sag, simply constructed bed springs will sag very quickly whilethe more expensive ones will, after use, acquire this defect,particularly if the spring frame is of the type that is used as a seat.In other words, the article of furniture is a sofa or seat that isconvertible to a bed. With such underlying supports, mattresses even ofthe inner-spring type, are never completely rigid in the longitudinaldirection and will thus conform themselves to the deformation of the bedsprings. Consequently the present constructions give rise to need for adefinite improvement particularly in the art of supports for mattressesand the like.

Present living conditions have a great influence on the necessity ofproviding more economically and structurally sound supporting structurefor beds, chairs and seats. In a great number of modern homes and inpractically every efiiciency apartment, convertible articles offurniture are in use, that is, those which are couches, settees ordivansin the daytime and are used as beds at night. Due to this rigorous use,the underlying supports for the seating or resting surface, particularlyits end and edges, should be comfortable enough to be embodied with aframe as to form a sag in the central portion thereof after use. Towithstand the rigors of double use as bed and for example couch, thestructure must be such as to withstand pressure occasioned during use byheavy persons without fatiguing or unduly straining the structure andstill be sufliciently comfortable as to not unduly fatigue the user.

The above mentioned factors indicate that a development along the linesof the following points is necessary, at least for beds available to thegeneral public.

(a) A spring bottom of a bedstead, hereinafter referred to as amattress, with absolute uniform elasticity along the whole of itssupporting surface, of a structure which cannot form a sag after usageand yet which is sufficiently yieldable or in other words, soft enoughto adapt itself to the contour of a recumbent human body, and

(b) A mattress of a simple and inexpensive type so as to be within theresources of the general purchasing public, yet which is essentiallyadapted to provide level and even support andproperly dispersedpressure. A mattress of this type will not sag or be deformed.

In order that the spring support or spring mattress of a bedstead mightfulfill the aforementioned desiderata, the following point should beadhered to in constructing the same:

1) Since in sleeping the human body should rest with its middle linestraight in a vertical plane, the elasticity of the supporting surfaceshould level the height differences between different body parts so thatthey are all properly supported and there is no undue pressure on thehip and shoulders,

(2) In order to prevent sag after usage, the supporting surface must beentirely separated from the end beams of its frame. Only with suchconstruction can full elasticity be attained at the head and foot endsof the structure,

(3) The supporting surface should comprise and have band-like members,transversely connected to the opposite side beams or components of theframe and independent of any connection to one another so that they canadjust themselves exactly to the contour of the body,

(4) The band-like members must be rigid in the direction transverse totheir length so that the application of force or a point of stress willnot force them apart so as to permit the hair-mattress or overlyingcushion to be forced or pressed into the spaces between the members.This requirement excludes known constructions of steel wire or coilsprings,

(5) The construction of steel bands must be such that even a strongoverloading, for example, when a person will stand on one single band,will not effect permanent deformation or fatigue in the material of theband members. This drawback is present when the supporting structure fora mattress or cushion utilizes coil springs. In the proper constructionwhen deformation even under stress has reached the maximum desiredvalue, it should automatically, gradually limit deformation, if possiblewithout the use of a positive stop or abutment,

(6) The supporting surface or upper surface of the structure should beelevated or raised above the beams or other frame components in unloadedcondition so that the sides and ends of the surface can be yieldable.Thus a thinner cushion or hair mattress can be used and still providefor comfortable seating.

(7) The various connections between the components should be such thatcreaking does not occur even after long usage and thus movableconnections between the components should be avoided,

that without legs, it does not weigh more than about 45 pounds,

(9) From the aesthetic viewpoint and in order to prevent wear of bedticking, the structures should be such that a cover canbe stretchedstraight-over the supporting surface without the cover being stretchedor slackened upon deflection of the surface,

(1-0) The construction should be simple, comprise relatively few parts,and which parts should be readily exchangeable in the event of need,

- :(ll) Cost of the structure should beeconomical so that the springmattress with'these desirable capabilities will meet the resources ofthe general public.

I The supporting surface should preferably bev-planar or flat inunloaded condition since a convex surface will give rise touncomfortable positioning of lighter body parts it they are ofinsufficient weight to press the 'sup-. porting surface into ahorizontal plane.

. It is accordingly an object of the present invention to provide amattress constructed with respect to the above noted viewpoints.

The spring mattress or supporting surface of this invention due tov itssimplicity and ability to withstand very great pressure changes forpractically an unlimited period of usage without altering its form orbecoming fatigued, renders it especially suitable in the constructionsof seats of various types. Accordingly the present invention provides asupporting surface that can be termed a spring mattress for use inupholstered seats, beds, settees, lounge chairs and the like, whichincludes a frame having opposite sides and ends, a plurality ofparallel, mutually spaced band-like members connected between theopposite sides of the frame, each band-like member consisting of tworesilient, curved steel bands, one at each end and an intermediate bandof a less high test material that connects with the inner ends of thetwo steel bands. The intermediate band is non-tensible in itslongitudinal directionand is straight in unloaded condition. Theconnection between-the curved steel bands and the frame ingludes.support members that are convexly curved on their entire surface withthe convexly curved portion underlying the steel bands. The steel bandsare capable of withstanding the entire springing stress upon theapplication of load and the convex curvature of the said supports beingsuch as to force the steel hands into rolling engagement therewith dueto. the application of load so that upon deflection ofthe bands they aresupported in a manner that the elastic limits of the bands are notexceeded, their free length, being successively decreased as differentportions come in contact with'the convex surface whereby upon deflectionup to a certain point the upper or terminal ends of the steel bands willreceive a component of movement; inward adjusted in its size, therebyestablishing a condition such that the intermediate bands connected atits opposite ends to the cueved steel bands can form a downwardlyextending parabolic curve. In accordance with'the modification of theinvention, the curved steel bands in the area adjacent the point ofconnection with, the intermediate bands are provided with a convexlyshaped upwardly-extended bent portion which is capable ofbeingresiliently straightened when; load is applied to the mattress and thesteel band is tensioned and which bent portion uponthe relief of theload returns to its original upwardly extending form. The advantageresulting from forming the curved steel band in this manner provides anarrangement in which the sides of the spring'mattress have a fullerandjmore attractiveappearance, and further presents a structurein whiehthesupporting surface upon application'of aheayy load will be somewhatmore comfortable or-softer than if the steel bands are in essentialstraight, since upon the app i ati o oad tot-t e ma tress the teel;ands; are. subj cted to as o aextensionstrainandia-straig t nins of thebands arises wherebyl-thedejath? oftheparabolic 4 curve of theintermediate bands must be somewhat increased under the maintenance ofthe absolute rigidity of the steel bands in the directions at rightangles to their length.

In order to provide a strong reliable and creak-free connection betweenthe pair of steel bands and the connecting intermediate band, the steelband on at least one side of the frame is provided at its inner end witha transversely extending slot, the adjacent end of the intermediate bandbeing provided with a down-turned end for cooperation with the slot andalso rearwardly of the down-turned end is a bent down tongue which afterthe down-turned end is passed through the slot in the steel band andbent'backwards the tongue is bent over the now bent back down-turnedend.

Further and more specific objects will be apparent from the followingdescription taken in connection with the ac companying drawingsillustrating several embodiments and in which:

Figure 1 is a fragmentary plan view of a resilient support or mattressfor a bed constructed in accordance with the invention,

Figure 2 is a transverse sectional view illustrating a side support, onecurved steel band and a portion of the intermediate band before it isconnected to the curved band,

Figure 3 is a fragmentary plan view of the two adjacent ends of one ofthe curved steel bands and a portion of the intermediate band,

Figure 4 is a longitudinal sectional view on an enlarged scale of aportion of the intermediate band and the adjacent portion of the curvedsteel band and illustrating the first stage of connecting the same,together,

Figure 5 is a, view similar to Figure 4 but illustrating the connectioncompleted,

Figure 6 is a fragmentary sectional view of one side of the support ormattress in unloaded condition,

Figure 7 is a transverse sectional view illustrating a side support andconnected thereto a steel band having a'convexly curved upwardly bentportion,

Figure 8 illustrates the structure of Figure 7 with the intermediateband connected thereto and in loaded condition,

Figure 9 is a transverse sectional view illustrating a tubular supportand a steel band having the upwardly bent portion adjacent its outerend,

Figure 10 is a fragmentary transverse sectional view illustrating aportion of a modified construction embodying additional spring means,

Figure 11 is a transverse sectional view of one of the supports anddiagrammatically illustrating one of the band-like members beforeassembly, in unloaded condition and during application of load,

Figure 12 is a transverse sectional view diagrammatically illustratingamattress in unloaded condition, and

Figure 13 is a similar view illustrating the mattress in loadedcondition.

As shown in Figure 1', the band-like resilient supporting elementsdenoted at 1 which constitute the supporting surface or mattress of abedstead are strained between longitudinal side beams 2 of the bottomframe, oneend beam 2a being illustrated. Each of the resilient membersis composed of three elementsa pair of curved steel bands 3 and anvintermediate band 4 of a less high test material, for example, bandiron. Each interme diate band 4 is-connected between a pair of curvedsteel bands. Theside beams 2 are provided with a longitudinallyextending slot- 6' extending inwardly from the outer side thereof andone-end ofeach curved steel band has an angularly bent portion 5 that isapertured at 8. The bentportion 5gisinserted inthe slot 6 and a woodscrew 77 fixes; each steel band: to the side beam 2 by passing throughtheiaperture 8, in the end- '5" of theband. The s, d.9.of; eachcurved-steel band isifixedtoone and ff the interme ate bands. 4.

' The opposite ends of each intermediate band 4, only one end beingshown in the drawing, are provided with a down-turned end portion 10.Inwardly of the downturned end there is provided a downwardly benttongue 11. As shown in Figure 2, the end of the intermediate band 4 isprovided with two longitudinally spaced tongue members extendingsubstantially at right angles to the plane of the band. The end portion9 of each steel band is provided with a transversely extending slot 12inwardly of the end and having a length that somewhat exceeds the widthof the intermediate band 4. The outer end of steel band 3 is providedwith a notch 13, the length of which slightly exceeds the width of thetongue 11. The construction of the mattress is effected as follows:

After the curved steel bands have been secured to the side frames 2 andthe intermediate bands 4 have been connected to the curved steel bands 3along one side of the frame, the steel bands 3 on the opposite side ofthe frame are bent inwardly, in Figure 2 to the right, to elfectconnection of the adjacent end of the intermediate band 4 therewith.This bending and connecting action is started at one end of the frameand the first curved steel band 3, for example, at the lower left handcorner of Figure l, is bent inwardly until it is possible to insert thedown-turned end portion of the band 4 in slot 12, Figure 4. At the sametime, the down-turned tongue 11 fits in the notch 13 and constitutes aguide for preventing mutual displacement of the interconnected partstransversely of their length. The down-turned end portion 10 is bentback to underlie the portion of the band 3 between notch 13 and slot 12andthen the tongue -11 is bent forwardly to underlap the bent backportion 10 as shown in Figure 5.

It is believed clear that in view of the overlapping of the tongue 11 informing the connection between the intermediate band 4 and the pair ofcurved steel bands 3, each of the band-like or resilient strips 1 can besubjected to considerable extension strains Without destroying theconnections. The connection is particularly strong and it does not creakwhen the mattress is in use. It is further clear that if for any reasonit is necessary to replace either an intermediate band or a curved steelband 3, the replacement can be effected very readily by bending backtongue 11 and the end part 10 with a suitable tool to disconnect theband 4 and after that is disconnected the removal of screw 7 will permitremoval of the curved steel band 3.

Each curved steel band is provided with a convex upwardly bent portion15. The end 14 of this bent portion is so adjusted that it will almostengage the rolling curve 16 on the upper, surface of the support 2 whenin fully loaded condition, Figure 8. According to the drawings, theupwardly bent convex portion is exposed to a strong extension strainwhen the mattress is fully loaded and this strain causes an elasticstraightening of the steel bands 3. When the load is relieved the bentportion 15 returns to the original upwardly extending form.

Wooden supporting beams 2 have been illustrated in the aforedescribedforms. If desirable, tubular supports 2 can be utilized, Figure 9. Thesetubular beams are provided with a longitudinal slot as at 18 to receiveone end of each of the steel bands 3'. The bands are provided with adown-turned bent end 17 which after insertion through the slot into thetube 2 will rest against the interior of the tube. Consequently when thebands are loaded, the offset end portion 17 will maintain them withinthe tube.

Figure 10 illustrates an embodiment in which the deflection of the steelbands is regulated by weaker supplementary springs or hands of aresilient, but in the directions of right angles to the length of thebands 3, rigid material. It is also possible to use less acclivity inthe rolling curve 16 while the major resistance against deflection ofthe bands 3 is provided by the additional spring, for example, the coilspring 19 illustrated. In the form 6 shown, the side beams are providedwith shouldered recesses 20 to accommodate the lower end of the springs19. The upper ends of the springs engage beneath the band-like members 1at the point 21.

Figure 11 illustrates one side support 2 with its rolling curved uppersurface 16. The relation between the ini-' tial bending radius R of thesteel band before assemblage on the support and the radius r isdetermined by the allowed maximum stress 7 according to the formula 2(rR in which 1. is the thickness of the steel band and E is the modulus ofelasticity of the material, usually ranging between about 28,800,000 and31,300,000 pounds per square inch. The chain-dotted curved line BC inFigure 11 shows how the end of the steel band 3 upon load is at firstmoved inwards a certain distance A whereby the distance between the twosteel bands of a pair is reduced so that the intermediate band 4 can nowform a downwardly bent parabolic curve, Figure 13. At the point C wherethe contact point of the band 3 against the upper curved surface 16 isabout level with the upper end of the steel band 3, a further depressionshould force the end of the band outward, which however is not possiblewithout a straightening of the parabolic curve and the lifting of theload as a result. Thus in the neighborhood of point C is attained asoftly acting stop against further depression of the supporting planewithout any sound causing engagement of parts, and an increased loadinvolves only a poor extension strain. Even now a certain elasticity ofthe supporting plane remains since upon side shifting of the load, forexample, if a person resting on the supporting surface turns on hisside, this movement forces the parabola to assume an irregular form.

in order that the supporting surface may softly conform itself to thebody form, the width of the steel springs 3 should not be larger thanthree inches and in order that the cushion or hair mattress be notforced into the spaces between the respective springing members 1, thelongitudinal edges of these members should not be too far apart. Eachband should be able to withstand about thirty-five pounds before thebottom position is reached. When a person is sitting on one side of thesupporting surface, each steel band should be able to withstand at least22-27 pounds. In order to be what is termed soft, the depression a ofthe side of the supporting surface should be at least %--1 inch. Themaximum depth of the parabola after the end of the pair of steel bandshas reached the stop position should be about 3 inches so that thesupporting surface may be comfortable. These figures, which of coursecan be varied according to the-aim and Wishes of the producer andcustomer, are determinative of the shape of construction.

The depth of the parabola f, Figure 13, is determined by the value of Aand L according to the formula in which the A is that distance measuredin the horizontal plane which the upper part of the steel band underload moves inwards while in contact with the beam 2 and L is the lengthof the intermediate band 4 connecting the steel bands 3, A being chosenbetween A and /2 inch and L between 10 and 40 inches. Thus at the normalwidth of a bed at 35 inches, the value of the A equals about /3 inch ata value of about 3 inches of the parabola depth is obtained. The angle vbetween the extension direction of the band-like member and thehorizontal plane at a stress point in the middle of the supportingsurface is obtained in each depression position by the formula (1)P=Drsin v and the bending moment of the steel band 2; M="" =D.--a (seeFig. 11

'in which a is the perpendicular distance from that point at which thesteel band leaves the curved surface of support 2 to that line denotedat 7', Figure 11, which indicatcs. the direction of force Dr at thepoint C. Upon sitting on the one side of. the supporting surface thecarrying capacity of the steel band at the end or stop position is (3:)W=% (see Fig. 11)

Upon the depression of the steel bands, the -value would first graduallyincrease with the unchanged length ofthe outerportion of the steel banduntil the maximum stress reaches the value settled by the relationbetween radius r and R when the rolling contact with the upper surfaceof beam 2 begins.

After that the 'y-value is determined by the relations between radius rand. Rand shortening of the steel band by'thedegree of curvature of therolling contact which can. be calculated for every depression or load.From the abovemoted Formulas 1 and 2, the t-value is obtained which'givesthe supporting surface the desired capabili- From the Formula 3,one obtains the freelength of the. steel band which furnishes thesoftness characteri'stic'de'sired. at the side. ofthe mattress. Thelength (1, Figure 11, of the free end of the steel band, that is thatportion between the end thereof and the initial end point of; contact,can be regulated by increasing the radius r and. R in relation to thelength of the steel band.

The full line through the point B illustrates the extension ofthe steelband member 3 in an unloaded condition'.

Since the values determined by the above-mentioned calculation,especially W-value, can be modified, one has the possibility of notingthe carrying capacity of the steel band during the first part ofdepression at a selected thickness t of the steel band so as to therebyinfluence the form of the curve of load.

There 'is another possibility of regulating the softness or resiliencyof the supporting surface within narrow limits by turning the supportingbeams 2 about their longitudinal axes and thus displacing the line D-E,Figure 11, which is always perpendicular to the horizontal, in acounterclockwise direction so as to, in accordance with the illustrationof Figure 11, move the contact point of the'steel band end with thesupport higher up on the curved surface 16 so that one obtains a smallera-value for the same A-value and thus resiliency is diminished. Bysimilarly turning in a clockwisedirection, that is moving the band withthe curved surface below the line passing through the center. of radiusr and R, Figure 11, a larger a-value is obtained which is tantamount toa more resilient'supporting surface. This possibility, however, islimited since it can furnish too large aA-value in relation to'thea-value (depression) desired.

Theinvention thus provides a very simple manner in which to obtain asupporting surface having resilient sides above a relatively rigidbottom frame and further to conform the abilities of the supportingframe to the desires of manufacturer and customer. The springiness iscompletely soundless and there is no risk of a permanent deformation inthe mattress or fatigue in the steel bands under rather abnormal loadconditions. person may stand on a single transverse band withoutbreaking or establishing any permanent deformation therein. An importantadvantage of the present invention is A rather heavy the softly andelastically limiting of the depression which isaccomplished without-anynoise: produciugcontact between parts. 'Since the resilient band-likemembers 1-are attached to the frame independently of one another, re-'placement and exchange of parts arerendered-very easily.

As stated above, upon the load being applied to the band-like members1,v the supports shall be such as to force the steel bands 3 intorollingengagement therewith without exceeding the elastic limits of thematerial of these steel bands. However, as the steel bands are exposedto a. certain fatigue strain, 'it issuitable to-dimension the steelbands so that they roll upon the supports'without exceeding thevariation in the maximum strain of the steel bands inorder to avoidfatigueat'the depression of the steel bands under load. The risk offatigue depends in essential on such a variation which is why theconstruction should be selected so that the maximum 'y-value, namely themaximum allowed deflection strain, is reached when the steel bands arestretched during the assembly and connection thereto of the bandironstraps 4. Consequently this maximum allowed; defiectionstrain' isnot changed during usage when the steelbands rollvup on the curvedsurface 16 but only that portion where the steel band is exposed tostrain is moved upwards along the support as the steel band comes intorolling contacttherewith.

It is further to be pointed out. that this invention comprehends anarrangement in. which the side frames 2 are jointed immediate of theirlength by hinges 'or thelike so that one half of the spring support canbe foldedon the other. In other words,. the invention contemplatesutility, in: those articles of: furniture 'known' as sofa beds orconvertible chairs wherein thespring support including the band-likemembers v1 and side frames are foldable. Thus the frame can be dividedinto any number. of parts which are hingedly connected with one another.

While some embodiments ofthe-present inventionhave been set forthherein, it isto beunderstood that modifications can-be employed so longas they do not'depart' from the scope of the appended claims. Ifdesired, one endof each intermediate band 4 can be bolted to one of thesteel bands 3 and the opposite end of the intermediate band can beprovided with the down-turned end portion 10 and the-tongue 11 and onlyone of the steel bands 3 provided with the slot 12 and the notch'13.

I give below detail characteristics of a preferred bandlike member 1 inrelation to its curved supporting surface adapted for a bedstead with awidth of about 35 inches measured from outer side-of left hand beamz toouter side of right hand beam 2.

The steel bands 3 are made of spring steel with arno'dulus of elasticityof E=28,845,000 pounds per square'inch, tensile strength of about242,000 pounds per square inch and (HO-0.80% C. Hardened in oil at 1760F.

Whole length of the steel band=4'inches.

Width of the steel band=2% inches.

Thickness of the steel baud=0.0354 inch.

Radius R (see Fig. '1l)=0.807 inch.

The intermediate band 4 is made of'coldqolled band iron, 0.20% C.

Whole length of the intermediate-band=33 inches.

Width of the intermediate band=1 A inches.

Thickness of the intermediate band= 7i inch.

Radius r (see Fig. 11) of the curvature of the supportsurface of thebeams=0.63 inch.

Calculation of the v -value ofthe steel bands 3:

y =l75,000 pounds per square in'ch.

Variation of 'y-Value'at the-difierent'points of the steel bands3duringrollin'gup on the supporting surface of the" beams should notexceed 71,20D-"-85,40'0' poundsper square inch:

The upwardly bent portion 15 (see Figures 7, 8 and 9) extends about 4inch above the main part of the steel band 3 when the latter is fixed tothe intermediate straight member 4 and the spring mattress is unloaded.

What is claimed is:

1. A resilient supporting surface for a spring mattress, upholsteredfurniture and the like comprising, a frame having opposite sides, aplurality of parallel, mutually spaced and laterally stilf band-likemeans extending between the sides of the frame and including oppositeends connected thereto, each said band-like means comprising at each endportion a curved spring steel band having an inner end, and between therespective inner ends of each opposed pair of curved spring steel bandsand connected thereto an intermediate band of a less high-test material,said intermediate band being non-tensible in its longitudinal directionand straight in unloaded condition, each of the opposite sides of theframes including means providing a rigid upper convex surface extendinginwardly and disposed adjacent the curved spring steel bands, the saidcurved spring steel bands having such strength and elastic capabilitiesas to withstand the entire spring stress upon application of load to theband-like means, the curved spring steel bands before assembly beingpre-set to a curvature of a radii greater than the radii of curvature ofthe rigid upper convex surfaces of the sides of the frame, theconnection between the inner ends of the curved spring steel bands andthe intermediate bands being located at a point substantially inwards ofthe high point of curvature of the respective rigid upper convexsurfaces and above the same, the connection between the outer ends ofthe curved spring steel band and the respective sides of the frame beinglocated in such relation to the different radii of curvatures of theunder surfaces of the curved spring steel bands and the upper convexsurfaces of the sides of the frame that when assembled and in unloadedcondition the under surface of each of the curved spring steel bandsstarts to recede from the rigid upper convex surfaces of the sides ofthe frame at a point on said curved upper convex surfaces that islocated approximately where the curvature of the convex surfaces of thesides of the frame commences to extend upwardly and inwardly toward thevertical plane through the high point of curvature of the upper surfacesof the sides of the frame, the curvature of the convex surfaces and thecurvature of the spring steel bands cooperating so that upon theapplication of load successive portions of the spring steel bands engagethe convex surfaces from the outer portion thereof upwardly and inwardlywith rolling contact without exceeding the elastic limit of the materialof the curved spring steel bands to decrease the free lengths thereof sothat upon deflection under load the ends of the curved spring steelbands at the points of connection with the intermediate bands receive apro-adjusted movement inwardly so as to shorten the distance between theopposite points of connection with the intermediate bands whereby thelatter form a downwardly bent parabolic curve, and said curved springsteel bands being pre-set so that during connection with theintermediate bands they reach approximately the allowed maximumdeflection strain to provide the supporting surface with the desiredstiffness in unloaded condition and to reduce fatigue-causing variationsin strain during usage when the spring steel bands make rolling contactwith the underlying convex surfaces thereby permitting a higher maximumstrain and lighter weight spring steel bands and with the result thateven upon application of an off-center load the rolling contactengagement of the curved spring steel band immediately commences andcontinues until equilibrium is reached when the pull of the spring steelbands changes its direction and thereby the nature of the rollingengagement is changed and with the lower limit of downward movement ofthe inner ends of the curved spring steel bands being attained when saidinner ends reach a point approximately level with the last point on therespective convex surfaces engaged by the under surface of the springsteel bands during the making of rolling contact with said convexsurfaces where the inward movement of the ends of the spring steel bandstends to reverse to outward movement thereby applying a stretching forceon the intermediate bands.

2. A resilient supporting surface for a spring mattress, upholsteredfurniture and the like comprising, a frame having opposite sides, aplurality of parallel, mutually spaced and laterally stiff band-likemeans extending between the sides of the frame and including oppositeends connected thereto, each said band-like means comprising at each endportion a curved spring steel band having an inner end, and between therespective inner ends of each opposed pair of curved spring steel bandsand connected thereto an intermediate band of a less high-test material,said intermediate band being non-tensible in its longitudinal directionand straight in unloaded condition, the opposite sides of the framesincluding means providing upper rigid convex surfaces extending inwardlyand disposed subjacent the curved spring steel bands, the said curvedspring steel bands having such strength and elastic capabilities as towithstand the entire spring stress upon application of load to theband-like means, the connection between the inner ends of the curvedspring steel bands and the intermediate bands being located at a pointsubstantially inwards of the high point of curvature of the respectiverigid upper convex surfaces and above the same, the connection betweenthe outer ends of the curved spring steel bands and the respective sidesof the frame being located in such relation to the different radii ofcurvatures of the under surfaces of the curved spring steel bands andthe upper convex surfaces of the sides of the frame that when assembledand in unloaded condition the under surface of each of the curved springsteel bands starts to recede from the rigid upper convex surfaces of thesides of the frame at a point on said curved convex surfaces that islocated approximately where the curvature of the convex surfaces of thesides of the frame commences to extend upwardly and inwardly toward thevertical plane through the high point of curvature of the upper surfacesof the sides of the frame, the curvature of the convex surfaces and thecurvature of the spring steel bands being different and cooperating sothat upon application of load successive portions of the spring steelbands engage the convex curved surfaces from the outer portion thereofupwardly and inwardly without exceeding the elastic limit of thematerial of the curved spring steel bands and to decrease the freelengths so that upon deflection under load the ends of the curved springsteel bands at the points of connection with the intermediate bandsreceive a pre-adjusted movement inwardly so as to shorten the distancebetween the opposite points of connection with the intermediate bandswhereby the latter form a downwardly bent parabolic curve, said curvedspring steel bands in the vicinity of the points of connection with theintermediate bands having a convexly upwardly bent portion capable ofbeing resiliently straightened at the tensioning of the spring steelbands under load and of returning to the original convexly upwardly bentform at release of the load.

3. A supporting surface as claimed in claim 2, in which end portions ofthe convexly upwardly bent portions of said spring steel bands remotefrom the points of connection with the intermediate bands are capable ofbeing brought into engagement with the supporting surfaces under a heavyload.

4. A resilient supporting surface for a spring mattress, upholsteredfurniture and the like comprising, a frame having opposite sides, aplurality of parallel, mutually spaced and laterally stiff band-likemeans extending between the sides of the frame and including oppositeends connected thereto, each said band-like means comprising at each endportion a curved spring steel band having an inner end, and between therespective inner ends of opposed pairs of curved spring steel bands andconnected thereto I1 an intermediate hand of a. lessflhigh-test-material,.:saidintermediate band being non-tensible in its.longitudinal direction and-straightiin'unloaded'condition, the oppositesides of the frames including means-providing upper convex surfacesextending inwardly and disposed subjacent the curved spring steel bands,the said curved spring steel bands having suchstrength and elasticcapabilities'as to withstand the entiresprin'g stress upon applicationof load to the band-like means, the curvature of the'convex surfaces andthe'curvature of the spring steel bands cooperating so that uponapplication of load successive portions of the spring steel bandsengage. the curved surfaces from the outer portion thereof upwardly andinwardly without exceeding the elastic limit of the material of'the.curved springsteel bands'and-to decrease the free lengths so thatupondefiection under load the'ends of the curved spring steel bands atthe points oficonnection with the intermediatelbands receive apre-adjustedmovement inwardly so as to shorten the distance between theoppositepoints of connection with the intermediate bands whereby thelatter form a downwardlybentparabolic curve, at least the curved springsteel bands connected to one of the side frames having a transverselyextending slot at the inner ends thereof, the adjacent end of eachintermediate band having a downwardly-bent endpassed through the slotand bent back toward the opposite side of the frame and tongue meansembodied with said intermediate band bent forwardly andunderlying theaforementioned bent end.

5. A supporting'surface as claimed in claim 4,.in which the tongue meansare integralwith the intermediate bands and pressed out of a portionthereof rearwardly adjacent the downwardly-bent ends.-

6. A. resilient supporting, surface. for. a spring mattress, upholsteredfurniture and the like comprising, a frame having; opposite sides, aplurality of iparallel, mutuallyspaced and laterally stiff band-likemeans extending betweenthe sides of the frame and including oppositeends connected thereto, each said band-like means comprising at each endportiona curved spring steel band; having an inner-end, and

between the respective inner ends ofopposed pairs of curved spring steelbands and connected thereto an intermediate metal band, saidintermediate bandbeing non- 1 2 tensible in? its longitudinal directionand straight in. unloaded. condition, the opposite sides of the'framesincluding means providing upper convex-surfaces extending inwardly anddisposed subjacent the curved-springsteel bands, the said curved springsteel bands havingsuch strength and elastic capabilities as' towithstand'the entire spring stress upon application of load to theband-like means, the curvature of the convex surfaces and the curvatureof'the spring steel bands cooperating so that upon application of loadsuccessive portions of the spring steel bands engage the curved surfacesfrom the outer portion thereof upwardly and inwardly without exceedingthe elastic limit of the material of the curved spring steel bands andto decrease the free lengths so that upon deflection under load-the.ends of the curved spring steel bands at the points of connection withthe intermediate bands receive a preadjusted movementinwardly so as toshorten the distance between the opposite points of connection with theintermediate bands whereby the latter form a downwardly bent ReferencesCited'in the file of this patent UNITED STATES PATENTS 26,235 'ScottNov. 22, 1859 155,530 Lord et a1. Sept. 29, 1874 2,667,916 Burd Feb. 2,1954 FOREIGN PATENTS 53,631 Austria May 25, 1912 102,728 Great BritainDec. 11, 1916 102,905 Germany May 3, 1899 308,973 Germany Nov. 7, 1918'350,061 France Aug. 30, 1905

